subs for LFT-8bs

In a recent post there was a recommendation for  Rhythmik subs to mate with these speakers - are any others recommended?  The problem I am having is I use these speakers for both music and movies -powered with quicksilver M60 monoblocks.  With dvds I have enough power but with blu-rays I am barely getting by - I was hoping the subs would improve the efficiency of my amps. thanks.
Moving more air with a sub will certainly make a minor difference,  but any way you look at it,  your speakers are like 83db sensitivity.  Anything playing that has a lower gain,  is going to give you some issues. If you are truly happy with the overall sound,  I would look for a player with variable output... if not,  a Preamp with a variable output..

thanks. using a computer as player - directly to amps - no preamp - was using a passive but this sounds better.  Sounds great - only issue is with blu rays - one solution would be to avoid blu ray altogether and just play dvds.  
Relieving your Quicksilver of bass frequencies will allow much more of it’s power to be available for the ET’s. That will require adding not just a sub or two, but a passive 1st order 6dB/octave high-pass filter (or active x/o) to the input jacks of the Quicksilver. All that entails is the installation of a capacitor on those jacks, which, if you lack soldering skills, can be done by any tech in five minutes. There is a formula for determining the value of the cap, involving the desired corner frequency and the input impedance of the amplifier. That formula can be found via a Google search. An active x/o, with steeper slopes (12/18/24 dB/octave), will remove more of the bass from the signal going into the Quicksilver, leaving more power for the ET’s. The Rythmiks are great with the ET’s, by the way.
Thank you, bdp24.  Would it be possible for me to contact you directly? 
Sure. I believe you can send me a pm through the Audiogon system.

Here’s the formula for determining the value of the capacitor (in pf) you need to solder onto your amp’s input jacks (the interior of the amp is the best location) to achieve the 6dB/octave filtering:

1/(2 x pi x f x 2), where f = the desired "corner" frequency of the filter.

100Hz maximum is typical, but you can go lower if you want less sub, higher if you want more power from your Quicksilver available for the ET’s. Many subs are not recommended above 100Hz (the mass of the woofer cone being too high), the Rythmik F12G one notable exception. Also, go above 100Hz only if you have stereo subs, as localization of the sub(s) will become audible above that, perhaps even AT 100Hz. The lower in distortion a sub, the less will it be audible as a separate sound source.

An active electronic sub with a steeper high pass filter (to the power amp) will make more power available for the ET’s, at the possible cost of a slight loss of transparency, depending on the quality of the x/o.

If you’re VERY ambitious, you could get a pair of the remarkable GR Research/Rythmik OB/Dipole Subs and use them in place of the stock ET 8" woofer, crossing-over at the factory 180Hz (the sub can be used up to an incredible 300Hz!). State-Of-The-Art bass reproduction!

Thank you, bdp24.  I don't believe I can send you a pm through this system, though.  
Oops! The formula is actually 1/(2 x pi x f x z), where f = desired frequency, and z = amp's input impedance. Misread my own writing!